For the first time in 10 Republican debates, Florida Sen. Marco Rubio owned the night.

With his back against the wall, yet to win a nominating contest, Rubio didn't prove he would be a better president, but by going toe-to-toe with Donald Trump showed he had improved as a debater. What a big mistake it was to lay off Trump for months, afraid of blowback. With nothing left to lose, Rubio stopped playing nice. It might be in time.

Rubio got his first digs in on immigration, attacking Trump's hiring of foreign workers instead of locals who wanted jobs at his hotels. The business tycoon paid a huge settlement for doing so. Rubio got even more personal on immigrant labor saying that if Trump were to build his wall along the Mexico border "the way he built Trump Tower, he'll be using illegal immigrants to do it."

Trump even took a hit on what he holds up as his greatest credential, his business acumen. After he referred to himself as the only person on stage who had ever hired anyone, Rubio made a crack about Trump's easy path to success. If his father hadn't left him "$200 million, you know where Donald Trump would be right now?" Rubio asked. "Selling watches in Manhattan."

Rubio made Trump look like a huckster who fleeces the little guy to make a buck. This line of attack had been underplayed in the campaign, despite sporadic articles tearing the bark off Trump's claim to being the world's best businessman creating millions of jobs. Rubio came at him about the defunct Trump University, which is now subject to several lawsuits, including a class-action by former students.

"There are people that borrow $36,000 to go to Trump University, and they're suing him now," Rubio said with delight. "And you know what they got? They got to take a picture with a cardboard cutout of Donald Trump."

Trump often looks angry but rarely timid as he did with his weak comeback that he'd "won most of the lawsuits" over the university.

Texas Sen. Ted Cruz played back-up band, turning the lying charge on Trump. "Falsely accusing someone of lying is a lie in itself." But with his finger-pointing intensity and inability to be human, Cruz didn't help himself as much as Rubio did.

Rubio's finest moment was a double whammy. He pulled off a very tricky self-deprecating attack, poking fun at himself for his disastrous performance in the previous debate, while mocking Trump for his this time.

When Trump reiterated the one specific of his health care plan -- allow insurers to compete across state lines -- Rubio said gleefully, "Guy's repeating himself." Trump volleyed by recalling Rubio's sweaty "meltdown" at the hands of New Jersey Gov. Chris Christie. "I thought he came out of a swimming pool."

But Rubio got the last word when Trump, shockingly, said the same thing about erasing state borders. "You repeated yourself five times five seconds ago." As Trump blithely went on, Rubio worked in Reagan's famous line against Jimmy Carter, "There you go again."

Trump showed flashes of anger but he never melted down. He remained nimble, thick-skinned and not slowed down by facts.

He turned left and right to insult Rubio and Cruz for desperately swinging for the fences. Neither, he said, could be president. "This guy's a choke artist," he turned to Rubio. "And this guy's a liar," he said turning to Cruz. Cruz's accomplishment of the night was to show that Trump's reason for not having released his tax returns -- that he was being audited by the Internal Revenue Service -- was weak.

Despite the wounds, Trump rallied in the last half hour, almost acting as if he were moderating the debate. He answered the charge he gave money to liberal Democrats by forcing Cruz to acknowledge that he got $5,000 from Trump and Rubio to concede that he inscribed a book he gave the Donald Trump with sweet nothings. When Cruz tried to grab back the spotlight, telling Trump to "relax," Trump reverted to form: "I'm relaxed. You're the basket case." He'd earlier told Cruz he should be ashamed of himself for having no friends.

The evening was so tense that Ohio Gov. John Kasich provided needed relief. Trump is fond of saying he's the only one on stage to have hired people, but that wasn't true. Kasich has hired, fired, created jobs and turned around depressed Ohio. He also was re-elected in a swing stage with 64 percent of the vote. In the latest USA Today poll, he beats Hillary Clinton. Maybe he will be the one to benefit from Rubio's wet work.

But if victory belongs to the dragon slayer, Rubio, who was leading in no Super Tuesday states coming into the debate, could surge to get his first win and consolidate the anti-Trump vote, even though he waited until the fourth quarter, when he was down 20 points, to go for broke. If Cruz loses Texas next week -- one poll has him ahead, two have him tied with Trump -- the way is cleared for Rubio to win Florida on March 15 and become the single challenger to Trump he's longed to be.

On Thursday night, he earned it.

Previously:

•02/24/16 Victorious Trump takes a stab at humility
•02/17/16 George W. Bush is a mixed blessing for Jeb
•02/11/16 Sanders should beware of a wounded Clinton
•02/10/16 Kasich is the Republicans' establishment outsider
•02/09/16 The governors upend the Republican debate
•02/03/16 Iowa is over. Now it gets interesting
•01/28/16 Trump does Republican voters a favor
•12/07/15 Christie's selling point: 'Anyone but Trump'
•11/12/15 Trump had a bad night in the Republican debate
•10/28/15 Politics is hard, but don't give up, Jeb
•10/21/15: Bush's battle with Rubio has a familiar plot
•10/12/15: Hillary's fake transparency has visible seams
•08/10/15: Predictions of Trump's death were exaggerated
•07/27/15: Kasich's Republican path to the White House
•06/15/15: Hey, Democrats, have you forgotten Joe Biden?

Margaret Carlson is a Bloomberg View columnist. A former White House correspondent for Time, she was also Time's first female columnist. She appeared on CNN's "Capital Gang" for 15 years. A former editor at the New Republic, Carlson has been a fellow at Harvard University's Institute of Politics, a Poynter Fellow at Yale University and a journalist-in-residence at the University of Notre Dame.